<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<script>
    'use strict'
    //用let表示局部变量
    let   i =1;
    alert(i);
    var jj = [1,2,4,5,"zjj",789]
</script>

</body>
</html>